Meteor Activity Outlook for April 25-May 1, 2009

Meteor activity picks up a bit during April as two major showers are active during the month. The first of these, the Lyrids, are active from the 16th through the 27th, with a pronounced maximum on the 22nd and 23rd. The Eta Aquariids start appearing near the 27th and reach maximum activity during the first week in May. Sporadic rates are low but steady as seen from the mid-northern hemisphere (45 N). Sporadic rates seen from the mid-southern hemisphere (45 S) rise this month toward a maximum in July.

During this period the moon reaches its new phase on Saturday April 25. At this time the moon lies close to the sun and is not visible at night. Later in the period the waxing crescent moon will enter the evening sky but will not interfere with meteor observing.The estimated total hourly rates for evening observers this week is near two as seen from the northern hemisphere and three for those situated south of the equator. For morning observers the estimated total hourly rates should be near ten for those located in the mid-northern hemisphere (45 N) and fifteen for those viewing from the mid-southern hemisphere (45 S). Locations between these two extremes would see activity between the listed figures. These rates assume that you are watching from rural areas away from all sources of light pollution. The actual rates will also depend on factors such as personal light and motion perception, local weather conditions, alertness and experience in watching meteor activity.

The radiant positions and rates listed below are exact for Saturday night/Sunday morning April 25/26. These positions do not change greatly day to day so the listed coordinates may be used during this entire period. Most star atlases (available at science stores and planetariums) will provide maps with grid lines of the celestial coordinates so that you may find out exactly where these positions are located in the sky. A planisphere or computer planetarium program is also useful in showing the sky at any time of night on any date of the year. Activity from each radiant is best seen when it is positioned highest in the sky, either due north or south along the meridian, depending on your latitude. It must be remembered that meteor activity is rarely seen at the radiant position. Rather they shoot outwards from the radiant so it is best to center your field of view so that the radiant lies at the edge and not the center. Viewing there will allow you to easily trace the path of each meteor back to the radiant (if it is a shower member) or in another direction if it is a sporadic. Meteor activity is not seen from radiants that are located below the horizon. The positions below are listed in a west to east manner in order of right ascension (celestial longitude). The positions listed first are located further west therefore are accessible earlier in the night while those listed further down the list rise later in the night.

The following showers are expected to be active this week:

The Pi Puppids (PPU) is a relatively new shower with most of the activity occurring when the parent comet (26P Grigg-Skjellerup) is near perihelion. This comet was last at perihelion in March 2008 so a trace of activity from this shower is not out of the question. The radiant for this shower lies far to the south and is nearly impossible to detect north of thirty degrees north latitude. The radiant position lies at 07:22 (111) -45. This area of the sky is located in southern Puppis, close to the third magnitude star Sigma Puppis. The radiant lies highest in a dark sky as soon as it becomes dark at the end of evening twilight. Peak activity occurred on April 23 so current rates are expected to be low, far less than one shower member hour. With an entry velocity of only 18 kilometers per second, these meteors will appear to move very slowly. Shower members are usually quite bright which may also aid in their identification.

The wide Antihelion (ANT) radiant is now centered at 15:12 (228) -18. This area of the sky lies in central Libra, two degrees north of the faint star Iota Librae. This radiant is best placed near 0200 LDT when it is located on the meridian and lies highest in the sky above the horizon. Due to the large size of this radiant, any meteor radiating from southeastern Virgo, Libra, extreme eastern Hydra, or western Scorpius could be a candidate for this shower. Rates at this time should be near two per hour as seen from the southern hemisphere and only one as seen from north of the equator. With an entry velocity of 30km/sec., the average Antihelion meteor would be of medium-slow speed.

The Lyrids (LYR) are the first major annual shower of the season. ZHR's reached one on April 16th and remain at or slightly above this level through April 27. The Lyrids peaked on Wednesday April 22 so current rates are falling and probably near one shower member per hour this weekend. The radiant currently lies at 18:20 (275) +34. This area of the sky is located in western Lyra, five degrees southwest of the brilliant zero magnitude star Vega (Alpha Lyrae). The radiant rises in the northeastern sky during the late evening hours for most locations in the Northern Hemisphere. The best time to view this activity is just before the start of morning twilight, when the radiant lies highest in a dark sky. With an entry velocity of 46 kilometers per second, a majority of these meteors will appear to move with moderate to swift speeds. The Lyrids are also known to produce a fair amount of meteors with persistent trains and an occasional fireball.

The video studies of Sirko Molau have revealed a weak radiant active in Cygnus this time of year. The Xi Cygnid (XCG) radiant is currently located at 21:04 (316) +43. This area of the sky is located in northeastern Cygnus, very close to the fourth magnitude star Xi Cygni. Maximum activity occurs on April 27 so current rates are expected to be near one per hour. These meteors are best seen during the last dark hour before dawn, when the radiant lies highest above the horizon in a dark sky. This shower is best seen from the northern hemisphere, where the radiant lies high in the sky at dawn. At 44 km/sec. the Xi Cygnids will usually produce meteors of medium velocity.

The Eta Aquariids (ETA) are particles from Halley's Comet, produced in Earth-crossing orbits many centuries ago. We pass closest to these orbits from May 5 through the 9th. During this period the Eta Aquariids are at their best, capable of producing ZHR's of sixty. The actual visible rates are most often less than half this figure due to the low altitude of the radiant at dawn. Observed hourly rates at maximum normally vary from zero at 60 degrees north latitude to 25 near the equator and back down to near zero again in Antarctica, where the radiant elevation is very low. Hourly rates are now anywhere from zero to two per hour depending on your latitude and observing conditions. The radiant is currently located at 21:52 (328) -05. This area of the sky is located in western Aquarius, four degrees west of the third magnitude star Sadalsuud (Beta Aquarii). The best time to view this activity is just before the start of morning twilight, when the radiant lies highest in a dark sky. No matter your location these meteors will appear from the eastern sky and shoot in all directions. If the radiant has sufficient altitude Eta Aquariid meteors can also be seen shooting down toward the eastern horizon. With an entry velocity of 68 kilometers per second, a majority of these meteors will appear to move swiftly with a high percentage of the bright meteors leaving persistent trains.

As seen from the mid-northern hemisphere (45N) one would expect to see approximately seven Sporadic meteors per hour during the last hour before dawn as seen from rural observing sites. Evening rates would be near two per hour. As seen from the mid-southern hemisphere (45S), morning rates would be near thirteen per hour as seen from rural observing sites and three per hour during the evening hours. Locations between these two extremes would see activity between the listed figures.

The table below presents a summary of the expected activity this week. Rates and positions are exact for Saturday night/Sunday morning but may be used all week.